There are a number of commercial processes for preparing N,N'-dialkylphenyl compounds using several synthesis steps. For example, U.S. Pat. No. 4,760,183 (Papenfuhs et al) describes a process of reducing aromatic nitro compounds to the corresponding amines, followed by reaction with an alkylating agent to replace the hydrogens on the amines with alkyl groups. A number of problems, including low yields and unwanted side reactions, are described for this process. The Papenfuhs et al patent then describes an alleged improvement using aldehydes as reductive agents in various solvents including alcohols. Catalytically activated hydrogen and precious metal catalysts are also used in the basic reaction environment.
Research Disclosure publication 37651 (August, 1995) describes the preparation of N-{4-(methylethyl)amino!phenyl}acetamide by reacting N-(4-nitrophenyl)acetamide in the presence of 5% platinum on carbon catalyst, acetone and ethanol. This step reduces the nitro group on the starting material to an amine. Alkylation during two steps adds two alkyl groups, with isolation between the two steps. The second step is carried out in the presence of diethylsulfate which is considered a carcinogenic material and is therefore difficult to handle. Besides the multiple steps and difficult reactants, this process provides low yields of 60-65%.
It would be desirable to have an improved process that requires less steps and hazardous materials, and provides improved yields.